tailieunhanh - Chapter 12: Cryptographic Hash Functions

Objectives of Chapter 12: To introduce general ideas behind cryptographic hash functions; to discuss the Merkle-Damgard scheme as the basis for iterated hash functions; to distinguish between two categories of hash functions; to discuss the structure of SHA-512; to discuss the structure of Whirlpool. | Cryptography and Network Security Jf Chapter 12 Cryptographic Hash Functions Chapter 12 Objectives To introduce general ideas behind cryptographic hash functions To discuss the Merkle-Damgard scheme as the basis for iterated hash functions To distinguish between two categories of hash functions To discuss the structure of SHA-512. To discuss the structure of Whirlpool. 12-1 INTRODUCTION A cryptographic hash function takes a message of arbitrary length and creates a message digest of fixed length. The ultimate goal of this chapter is to discuss the details of the two most promising cryptographic hash algorithms SHA-512 and Whirlpool. Topics discussed in this section Iterated Hash Function Two Groups of Compression Functions Two Groups of Compression Functions 1. The compression function is made from scratch. Message Digest MD 2. A symmetric-key block cipher serves as a compression function. Whirlpool Continued Table Characteristics of Secure Hash Algorithms SHAs Characteristics SHA-I SHA-224 SHA-256 SHA-384 SHA-512 Maximum Message size 264_j 204- 1 1 2128_ 2 28-l Block size 512 512 512 1024 1024 Message digest size 160 224 256 384 512 Number of rounds 80 64 64 80 80 Word size 32 32 32 64 64 1 Continued Continued Rabin Scheme Davies-Meyer Scheme Figure Rabin scheme Figure Davies-Meyer scheme Continued Matyas-Meyer-Oseas Scheme Continued I Miyaguchi-Preneel Scheme Figure Matyas-Meyer-Oseas scheme Figure Miyaguchi-Preneel scheme 12-2 SHA-512 Introduction SHA-512 is the version of SHA with a 512-bit message digest. This version like the others in the SHA family of algorithms is based on the Merkle-Damgard scheme. Topics discussed in this section Figure Message digest creation SHA-512 Introduction Compression Function Analysis 2 Continued Continued Message Preparation SHA-512 insists that the length of the original .

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